Substrate processing apparatus

ABSTRACT

A substrate processing apparatus of the invention includes: a substrate holding unit that holds a substrate almost in a horizontal posture; a rotating unit that rotates the substrate held by the substrate holding unit about a vertical shaft line; and an etching liquid nozzle disposed oppositely to a bottom surface of the substrate held by the substrate holding unit and having plural discharge ports each having a different distance from a rotation center of the substrate rotated by the rotating unit so as to discharge an etching liquid toward the bottom surface of the substrate rotated by the rotating unit from the plural discharge ports.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate processing apparatus that etches away a surface of a substrate using an etching liquid. Substrates subjected to etching include but not limited to a semiconductor wafer, a glass substrate for liquid crystal display, a glass substrate for plasma display, a substrate for FED (Field Emission Display), an optical disc substrate, a magnetic disc substrate, a magneto optical disc substrate, and a photomask substrate.

2. Description of Related Art

In the fabrication sequence of a semiconductor device, liquid processing using a processing liquid is applied to a semiconductor wafer. One of such liquid processing is etching processing in which an etching liquid is supplied to a surface of the semiconductor wafer. The etching processing referred to herein includes, besides etching processing to form a pattern on a surface of a semiconductor wafer (the semiconductor wafer itself or a thin film formed on the semiconductor wafer), rinse processing to remove foreign matter on a surface of the semiconductor wafer by utilizing an etching action.

A substrate processing apparatus that processes a semiconductor wafer using a processing liquid includes a batch type configured to apply processing to plural semiconductor wafers collectively at a time and a single substrate process type configured to apply processing to semiconductor wafers one by one. The single substrate process type substrate processing apparatus has a spin chuck that rotates while holding a semiconductor wafer almost in a horizontal posture, and a processing liquid nozzle that supplies a processing liquid toward a surface of the semiconductor wafer held by the spin chuck.

In a case where the processing liquid is supplied to the bottom surface of the semiconductor wafer held by the spin chuck, a center shaft nozzle inserted through the rotation shaft of the spin chuck is used. A discharge port at an upper end of the center shaft nozzle opposes the center of the bottom surface of the semiconductor wafer held by the spin chuck. When the processing liquid discharged from the discharge port reaches the bottom surface of the semiconductor wafer, the processing liquid spreads toward the outer side along the rotation radius direction under a centrifugal force. The processing liquid is thus supplied across the entire bottom surface of the semiconductor wafer.

For example, in a case where the etching processing is to be applied to a semiconductor wafer on the device forming surface, the semiconductor wafer is held by the spin chuck with the device forming surface faced down. The semiconductor wafer is rotated about a vertical shaft line by the spin chuck and the etching liquid is discharged from the center shaft nozzle toward the rotation center of the device forming surface. The etching liquid having reached the device forming surface of the semiconductor wafer migrates toward the outer side along the rotation radius direction under a centrifugal force induced by rotations of the semiconductor wafer, and is consequently supplied across the entire surface of the device forming surface of the semiconductor wafer (see, for example, Japanese Unexamined Patent Publication No. 2002-110626 and United States Patent Application Publication No. US2003/0194878A1).

The etching liquid supplied to the semiconductor wafer, however, spreads radially about a region where it was supplied, and because the spreading direction of the etching liquid supplied to the rotation center of the semiconductor wafer coincides with the acting direction of the centrifugal force, the etching liquid hardly drops off while it migrates toward the peripheral edge of the semiconductor wafer. Accordingly, a large amount of the etching liquid reaches the peripheral edge of the semiconductor wafer. In this case, the etching liquid may possibly flow over from the peripheral edge of the semiconductor wafer onto the surface (top surface) on the opposite side and undesirably etch away the surface on the opposite side.

In particular, in a case where a mechanical chuck that holds a semiconductor wafer by pinching the peripheral edge of the semiconductor wafer using plural pinching members is used as the spin chuck, because the etching liquid flows over onto the surface on the opposite side by running along plural pinching members, etching proceeds particularly in portions abutted on the pinching members, which raises a problem that plural traces of etching (so-called pin marks) are left along the peripheral edge of the semiconductor wafer.

SUMMARY OF THE INVENTION

An object of the invention is therefore to provide a substrate processing apparatus not only capable of applying etching processing across the entire bottom surface of the substrate, but also capable of suppressing or preventing an etching liquid supplied to the bottom surface of the substrate from flowing over onto the top surface.

A substrate processing apparatus of the invention includes: a substrate holding unit that holds a substrate almost in a horizontal posture; a rotating unit that rotates the substrate held by the substrate holding unit about a vertical shaft line; and an etching liquid nozzle disposed oppositely to a bottom surface of the substrate held by the substrate holding unit and having plural discharge ports each having a different distance from a rotation center of the substrate rotated by the rotating unit so as to discharge an etching liquid toward the bottom surface of the substrate rotated by the rotating unit from the plural discharge ports.

According to this configuration, the etching liquid discharged from the plural discharge ports in a distributed manner is supplied directly to the bottom surface of the substrate in plural regions each having a different distance from the rotation center thereof. The etching liquid supplied to the plural supplied regions on the bottom surface of the substrate spreads radially about the respective supplied regions. The etching liquid spreading toward the rotation center drops off by a centrifugal force induced by rotations of the substrate, whereas the etching liquid spreading toward the peripheral edge drops off as the etching liquid under consideration interferes with the etching liquid supplied to regions closer to the peripheral edge of the substrate than the supplied region of the etching liquid under consideration. An amount of the etching liquid reaching the peripheral edge of the substrate is therefore relatively small. Hence, not only is it possible to apply the etching processing across the entire bottom surface of the substrate, but it is also possible to suppress or prevent the etching liquid from flowing over onto the top surface of the substrate.

It is preferable that the plural discharge ports of the etching liquid nozzle are provided in such a manner that discharge flow rates of the etching liquid per unit area on the bottom surface of the substrate that is being rotated by the rotating unit become equal almost entirely across the bottom surface of the substrate.

According to this configuration, the discharge flow rates of the etching liquid per unit area on the bottom surface of the substrate are equal almost entirely across the bottom surface of the substrate. It is thus possible to supply a fresh etching liquid directly and uniformly almost across the entire bottom surface of the substrate.

In a case where an etching liquid having extremely high etching power when it is fresh but deteriorating so fast that it loses etching power almost completely in an instant is used, when the etching liquid is supplied to the substrate, the etching rate is quite high in the supplied regions, whereas the etching rate is low in the other regions. However, even when such an etching liquid is used, because a fresh etching liquid is supplied directly and uniformly almost across the substrate, it is possible to etch away the entire bottom surface of the substrate uniformly at an extremely high etching rate. As the etching liquid supplied from the etching liquid nozzle, for example, hydrofluoric-nitric acid can be used.

It is preferable that the plural discharge ports of the etching liquid nozzle are aligned along a rotation radius direction of the substrate rotated by the rotating unit.

According to this configuration, it is possible to supply a fresh etching liquid directly almost across the entire bottom surface of the substrate that is rotating.

Also, it is preferable that the plural discharge ports of the etching liquid nozzle are disposed more densely with distance from the rotation center of the substrate rotated by the rotating unit.

According to this configuration, discharge flow rates of the etching liquid discharged toward the substrate from the etching liquid nozzle increases with distance from the rotation center of the substrate. Meanwhile, the positions on the bottom surface of the substrate at which the etching liquid is supplied move at a higher speed with distance from the rotation center. Consequently, a fresh etching liquid discharged from the plural discharge ports is supplied directly to the bottom surface of the substrate in such a manner that discharge flow rates of the etching liquid per unit area become equal.

It may be configured in such a manner that the plural discharge ports of the etching liquid nozzle are aligned along a rotation radius direction at almost same density so as to oppose a region from a center to a peripheral edge of the substrate rotated by the rotating unit.

The center of the substrate referred to herein means a region in close proximity to the rotation center of the substrate.

According to this configuration, because the etching liquid is supplied to the substrate from the plural discharge ports aligned at almost the same density, discharge flow rates of the etching liquid discharged to the bottom surface of the substrate from the etching liquid nozzle are almost equal from the center to the peripheral edge of the substrate. The etching liquid discharged from the respective discharge ports therefore interferes with one another to a moderate degree, which further reduces an amount of the etching liquid reaching the peripheral edge of the substrate. It is thus possible to further suppress the etching liquid from flowing over onto the top surface of the substrate.

Also, it is preferable that the plural discharge ports of the etching liquid nozzle include plural peripheral discharge ports aligned along a rotation radius direction almost at same density so as to oppose a region of the substrate rotated by the rotating unit excluding a center thereof.

According to this configuration, because the etching liquid is supplied to the substrate from the plural peripheral discharge ports aligned along the rotation radius direction at almost the same density, discharge flow rates of the etching liquid discharged to the bottom surface of the substrate from the etching liquid nozzle are almost equal except for the center of the substrate. The etching liquid discharged from the respective discharge ports therefore interferes with one another to a moderate degree. An amount of the etching liquid reaching the peripheral edge of the substrate is thus reduced further. Consequently, it is possible to further suppress the etching liquid from flowing over onto the top surface of the substrate.

Further, by omitting the discharge port in a region opposing the center of the bottom surface of the substrate or by disposing the discharge ports in this region less densely than the peripheral discharge ports, discharge flow rates of the etching liquid become lower at the center of the bottom surface of the substrate than in the other regions. It is thus possible to suppress an increase of the etching rate at the center of the substrate where the respective positions on the bottom surface of the substrate move at a relatively slow speed. Consequently, it is possible to apply the etching processing uniformly across the entire bottom surface of the substrate.

In a case where the discharge port opposing the center of the bottom surface of the substrate is provided to the etching liquid nozzle, it is preferable to provide the discharge port at a position displaced from the position opposing the rotation center of the bottom surface of the substrate in the rotation radius direction of the substrate. In this case, because the etching liquid is not supplied directly to the rotation center of the bottom surface of the substrate, it is possible to suppress an abrupt increase of the etching rate at the rotation center of the substrate. In addition, in this case, it is more preferable to dispose the discharge port at a position at which it is possible to supply the etching liquid to the rotation center of the bottom surface of the substrate as the etching liquid spreads when the etching liquid reaches the bottom surface of the substrate.

It is preferable that the plural discharge ports include a discharge port for peripheral edge to supply the etching liquid to a peripheral edge of the substrate rotated by the rotating unit and plural inner discharge ports disposed closer to the rotation center of the substrate than the discharge port for peripheral edge, and that the discharge port for peripheral edge includes a larger diameter discharge port having a larger diameter than the inner discharge ports.

According to this configuration, a discharge flow rate of the etching liquid of the discharge port for peripheral edge is higher than the discharge flow rates of the inner discharge ports. Hence, discharge flow rates of the etching liquid become higher in the peripheral edge of the bottom surface of the substrate than in the inner regions thereof. It is thus possible to suppress a decrease of the etching rate in the peripheral edge of the substrate where the respective positions on the bottom surface of the substrate move relatively at a high speed. Consequently, it is possible to apply the etching processing uniformly across the entire bottom surface of the substrate.

Also, it is preferable that the plural discharge ports include a discharge port for peripheral edge to supply the etching liquid to a peripheral edge of the substrate rotated by the rotating unit, and that the discharge port for peripheral edge has an inclined discharge port that discharges the etching liquid in a direction inclined outward in a radius direction of the substrate with respect to a vertical direction.

According to this configuration, the etching liquid is discharged in a direction inclined outward in the radius direction of the substrate with respect to the vertical direction. Hence, even in a case where the tip end of the etching liquid nozzle is located at the position inner than the peripheral edge of the substrate, it is possible to supply the etching liquid directly to the peripheral edge of the substrate.

The substrate processing apparatus may be configured to further include an etching liquid heating unit that heats the etching liquid to be discharged from the plural discharge ports of the etching liquid nozzle.

According to this configuration, a heated etching liquid is discharged from the plural discharge ports of the etching liquid nozzle. The heated etching liquid has high etching power. It is therefore possible to etch away the bottom surface of the substrate at a high etching rate.

The substrate holding unit may include plural holding members that hold the substrate almost in the horizontal posture in cooperation by abutting on a peripheral edge of the substrate at different positions.

According to this configuration, because an amount of the etching liquid reaching the peripheral edge of the substrate is relatively small, even in a case where plural holding members are used to hold the substrate, the etching liquid hardly flows over onto the top surface of the substrate by running along the holding members. It is thus possible to hold the substrate appropriately without leaving plural traces of etching along the peripheral edge on the top surface of the substrate.

The above and other objects, features, and advantages of the invention will become more apparent from the following description of embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section schematically showing the configuration of a substrate processing apparatus according to a first embodiment of the invention;

FIG. 2 is a plan view of a spin chuck in the substrate processing apparatus shown in FIG. 1;

FIG. 3 is a plan view of an etching liquid nozzle in a substrate processing apparatus according to a second embodiment of the invention;

FIG. 4 is a longitudinal cross section showing the configuration of a major portion of the etching liquid nozzle of FIG. 3;

FIG. 5 is a graph showing an in-plane distribution of etching amounts in etching tests;

FIG. 6 is a view showing flown over amounts of the etching liquid in the etching tests;

FIG. 7 is a plan view of a spin chuck in a substrate processing apparatus according to a third embodiment of the invention;

FIG. 8 is a plan view showing a spin chuck in a substrate processing apparatus according to a fourth embodiment of the invention;

FIG. 9 is a plan view of the spin chuck in the substrate processing apparatus shown in FIG. 8; and

FIG. 10 is a plan view of a spin chuck in a substrate processing apparatus according to a fifth embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a cross section schematically showing the configuration of a substrate processing apparatus 300 according to one embodiment (first embodiment) of the invention.

The substrate processing apparatus 300 is a single substrate process type apparatus that applies etching processing for removing an oxide film to the surface (bottom surface) 9 on the device forming region side of a disc-shaped semiconductor wafer (hereinafter, referred to simply as the wafer) W formed of, for example, an oxide film silicon wafer. In this embodiment, for example, hydrofluoric acid is used as an etching liquid.

The substrate processing apparatus 300 includes a spin chuck 301 as a substrate holding unit that rotates about a vertical shaft line (rotation shaft line) 1 a passing almost the center of the wafer W while holding the wafer W almost in a horizontal posture.

FIG. 2 is a plan view schematically showing the configuration of the spin chuck 301 of the substrate processing apparatus 300 shown in FIG. 1.

Referring to FIG. 1 and FIG. 2, the spin chuck 301 has a disc-like spin base 302. Plural (six in this embodiment) pinching members 303 are disposed at almost equiangular intervals along the peripheral edge on the top surface of the spin base 302. The wafer W is held almost in a horizontal posture as the plural pinching members 303 pinch the peripheral edge of the wafer W. While holding the wafer W, each pinching member 303 abuts on the end face of the wafer W and the peripheral edge on the bottom surface 9 of the wafer W.

The spin base 302 is configured to rotate by being coupled to the top end of a rotation shaft 305 that is rotated by a chuck rotary driving mechanism 304 including a motor. The rotation shaft 305 is a hollow shaft, inside of which an insertion tube 306 is inserted through. The insertion tube 306 is held inside the rotation shaft 305 in a non-rotating state.

An etching liquid nozzle 307 in the shape of a straight line when viewed in a plane is disposed on the spin base 302. The etching liquid nozzle 307 is a long nozzle extending along the rotation radius direction of the wafer W by passing through the rotation center C of the wafer W. In order to prevent interference of the etching liquid nozzle 307 with the pinching members 303 during rotations of the spin base 302, the both ends of the etching liquid nozzle 307 are stopped at positions slightly inner than the peripheral edge of the spin base 302. The both ends of the etching liquid nozzle 307 are therefore located on the inner side than the end face of the wafer W held by the spin chuck 301.

The etching liquid nozzle 307 is made hollow inside and linked to the insertion tube 306 at the center position of the bottom thereof. The etching liquid nozzle 307 therefore remains stationary and will never rotate in association with rotations of the spin base 302.

A rotation shaft discharge port 311 disposed on the rotation shaft axis (vertical shaft line) 1 a of the wafer W and a pair of peripheral discharge port groups 310 disposed with the rotation shaft discharge port 311 in between are provided to the top surface of the etching liquid nozzle 307. Each peripheral discharge port group 310 includes plural peripheral discharge ports 312 each having a different distance from the rotation center C of the wafer W. The plural peripheral discharge ports 312 are aligned along the shape of the etching liquid nozzle 307 (along the rotation radius direction of the wafer W). The plural peripheral discharge ports 312 are disposed at regular intervals (at the same density, that is, isopycnic) in a region opposing a region of the wafer W excluding the rotation center C thereof. The etching liquid is discharged upward (vertical direction) from the respective discharge ports 311 and 312.

In this embodiment, an interval between each peripheral discharge port 312 adjacent to the rotation shaft discharge port 311 and the rotation shaft discharge port 311 is set to a length equal to an interval between one peripheral discharge port 312 and another peripheral discharge port 312. In other words, the discharge ports 311 and 312 are disposed at regular intervals (at the same density) from one end to the other end of the etching liquid nozzle 307.

In Example 1 described below in which an experiment for trial production was conducted by the inventor of the present application, the length of the etching liquid nozzle 307 was set to 272 mm, the diameter of the discharge ports 311 and 312 was set to 0.5 mm, and the interval among the respective discharge ports 311 and 312 was set to 5 mm.

In addition, a supply channel 313 extending linearly along the shape of the etching liquid nozzle 307 and communicating with the respective discharge ports 311 and 312 is formed inside the etching liquid nozzle 307.

A circulation channel 314 is formed inside the insertion tube 306 along the rotation shaft line 1 a. The circulation channel 314 communicates with the supply channel 313. A collecting supply tube 30 is connected to the circulation channel 314. An etching liquid supply tube 27, to which the etching liquid is supplied from an etching liquid supply source, is connected to the collecting supply tube 30. An etching liquid valve 315 and a heater 28 to heat the etching liquid circulating through the etching supply tube 27 are interposed in midstream of the etching liquid supply tube 27 sequentially in this order from the etching liquid supply source side. When the etching liquid valve 315 is opened, the etching liquid circulates through the etching liquid supply tube 27, and the etching liquid heated to 40 to 80° C. by the heater 28 while being circulated is supplied to the circulation channel 314. In addition, a deionized water supply tube 29, to which deionized water is supplied from a deionized water supply source, is connected to the collecting supply tube 30. A deionized water valve 316 is interposed in midstream of the deionized water supply tube 29 for deionized water to be supplied to the circulation channel 314.

According to the configuration as above, by closing the deionized water valve 316 and opening the etching liquid valve 315, it is possible to supply the etching liquid heated to 40 to 80° C. to the rotation shaft discharge port 311 and the peripheral discharge ports 312 of the etching liquid nozzle 307 via the circulation channel 314 and the supply channel 313. Conversely, by closing the etching liquid valve 315 and opening the deionized water valve 316, it is possible to supply deionized water to the rotation shaft discharge port 311 and the peripheral discharge ports 312 of the etching liquid nozzle 307 via the circulation channel 314 and the supply channel 313.

A gas supply channel 317 is defined between the inner wall surface of the rotation shaft 305 formed of a hollow shaft and the outer wall surface of the insertion tube 306. The gas supply tube 317 opens to the top surface of the spin base 302. It is configured in such a manner that a nitrogen gas as an inert gas is supplied to the gas supply channel 317 via a nitrogen gas valve 318.

A disc-shaped shield plate 320 having substantially the same diameter as the wafer W is provided above the spin chuck 301. The shield plate 320 has an opening 319 at the center thereof. A rotation shaft 321 extending along a shaft line common with the rotation shaft line 1 a of the spin chuck 301 is fixed to the top surface of the shield plate 320. The rotation shaft 321 is made hollow, inside of which is formed a gas supply channel 323 that communicates with the opening 319 in the shield plate 320 and thereby supplies a nitrogen gas toward the center of the wafer W. It is configured in such a manner that a nitrogen gas is supplied to the gas supply channel 323 via a nitrogen gas valve 324.

The rotation shaft 321 is provided with a shield plate elevation driving mechanism 325 to move the shield plate 320 up and down between a proximity position at which the shield plate 320 comes in close proximity to the top surface of the wafer W held by the spin chuck 301 and an evacuation position at which the shield plate 320 evacuates far above the spin chuck 301, and a shield plate rotary driving mechanism 326 to rotate the shield plate 320 almost in sync with rotations of the wafer W by the spin chuck 301.

Hereinafter, etching processing applied to the bottom surface 9 of the wafer W in the substrate processing apparatus 300 will be described.

Before the wafer W subjected to processing is carried into the substrate processing apparatus 300, the shield plate 320 is located at the evacuation position at which it evacuates far above the spin chuck 301 so as not to interrupt a carry-in operation.

In order to process the wafer W, the wafer W is first carried into the substrate processing apparatus 300 by an unillustrated delivery robot, and the wafer W is held by the spin base 302 of the spin chuck 301 with the surface on the device forming region side faced down. When the wafer W is held by the spin base 302, the chuck rotary driving mechanism 304 is controlled for the spin base 302 to start to rotate the wafer W, and the rotating speed of the wafer W is increased, for example, to 1000 rpm. In this instance, the etching liquid nozzle 307 remains stationary as has been described above and will never rotate in association with rotations of the spin base 302. Also, the shield plate elevation driving mechanism 325 is controlled for the shield plate 320 to move down to the proximity position at which it comes in close proximity to the top surface of the wafer W held by the spin base 302. The shield plate rotary driving mechanism 326 is then controlled for the shield plate 320 to keep rotating in the same direction as the wafer W, while the nitrogen gas valve 324 is opened for a nitrogen gas to be supplied from the opening 319 in the shield plate 320 to a space between the wafer W and the shield plate 320. Accordingly, a current of nitrogen gas flowing outward in the radial direction from the center of the shield plate 320 is produced in the space between the wafer W and the shield plate 320.

When the rotating speed of the wafer W reaches, for example, 1000 rpm, the etching liquid valve 315 is opened, and the etching liquid heated to 40 to 80° C. is discharged from the rotation shaft discharge port 311 and the respective peripheral discharge ports 312 of the etching liquid nozzle 307 toward the bottom surface 9 of the wafer W that is rotating. The nitrogen gas valve 318 is also opened and a nitrogen gas is supplied to a space surrounded by the spin base 302 and the bottom surface 9 of the wafer W.

The etching liquid discharged from the rotation shaft discharge port 311 is supplied directly to the rotation center C of the bottom surface 9 of the wafer W. The etching liquid discharged from the respective peripheral discharge ports 312 is supplied directly to the bottom surface 9 of the wafer W opposing the respective peripheral discharge ports 312. Because the discharge ports 311 and 312 are disposed at regular intervals, discharge flow rates of the etching liquid discharged directly to the bottom surface 9 of the wafer W are almost equal from the center (a region in close proximity to the rotation center C) to the peripheral edge of the wafer W.

The etching liquid discharged from the respective discharge ports 311 and 312 are relatively hot at 40 to 80° C. in comparison with normal temperature. Etching power of the etching liquid is therefore high. Because the etching liquid having high etching power is supplied directly across the entire bottom surface 9 of the wafer W, almost the entire bottom surface 9 of the wafer W is etched away at a high etching rate.

The etching liquid supplied to the bottom surface 9 of the wafer W from the respective discharge ports 311 and 312 spreads radially about the corresponding supplied regions, and then migrates over the bottom surface 9 toward the peripheral edge of the wafer W as it experiences a centrifugal force induced by rotations of the wafer W to be wasted to the outside of the wafer W from the peripheral edge.

The etching liquid supplied to the respective supplied regions and then spreading toward the rotation center C falls down because of a centrifugal force induced by rotations of the wafer W, whereas the etching liquid spreading toward the peripheral edge of the wafer W falls down as the etching liquid under consideration interferes with the etching liquid supplied to regions closer to the peripheral edge than the supplied region of the etching liquid under consideration. In particular, because discharge flow rates of the etching liquid discharged directly to the bottom surface 9 of the wafer W are almost equal from the center to the peripheral edge of the wafer W, etching liquid discharged from the respective peripheral discharge ports 312 interferes with one another to a moderate degree. Hence, in comparison with an amount of the etching liquid supplied to the bottom surface 9 of the wafer W, an amount of the etching liquid reaching the peripheral edge of the wafer W is small.

Also, a current of nitrogen gas flowing outward in the radial direction from the center of the shield plate 320 is produced in the space between the wafer W (top surface) and the shield plate 320. It is therefore difficult for the etching liquid flowing toward the peripheral edge of the wafer W to flow over onto the top surface of the wafer W. It is thus possible to further suppress or prevent the etching liquid from flowing over onto the top surface of the wafer W.

When a predetermined time (for example, one minute) has elapsed since the supply of the etching liquid started, the etching liquid valve 315 is closed. The deionized water valve 316 is then opened for deionized water to be supplied across the entire bottom surface 9 of the wafer W from the rotation shaft discharge port 311 and the peripheral discharge ports 312. The rotating speed of the wafer W is reduced, for example, from 1000 rpm to 500 rpm. In this instance, deionized water discharged from the rotation shaft discharge port 311 is supplied directly to the rotation center C of the bottom surface 9 of the wafer W. Deionized water discharged from the respective peripheral discharge ports 312 is supplied directly to regions on the bottom surface 9 of the wafer W opposing the respective peripheral discharge ports 312.

Deionized water supplied to the bottom surface 9 of the wafer W flows toward the peripheral edge of the wafer W owing to a centrifugal force induced by rotations of the wafer W. Deionized water is then wasted to the outside from the peripheral edge of the wafer W. The etching liquid adhering onto the bottom surface 9 of the wafer W is thus rinsed away by deionized water.

A current of nitrogen gas flowing outward in the rotation radial direction of the wafer W from the center of the shield plate 320 is produced in the space between the wafer W (top surface) and the shield plate 320. It is thus possible to suppress or prevent a mixed liquid of deionized water and the etching liquid from flowing over onto the top surface of the wafer W.

When a predetermined time (for example, 30 seconds) has elapsed since the supply of deionized water started, the deionized water valve 316 is closed to stop the supply of deionized water to the bottom surface 9 of the wafer W. In addition, the nitrogen gas valve 324 is closed and the shield plate elevation driving mechanism 325 is controlled for the shield plate 320 to move up to the evacuation position at which it evacuates far above the spin chuck 301.

The rotating speed of the wafer W is then increased from 500 rpm to 2500 rpm to apply spin dry processing in which the wafer W is dried by throwing off deionized water adhering onto the surface thereof using a centrifugal force after the water rinse processing. When the spin dry processing is applied over, for example, 120 seconds, the wafer W is stopped rotating, and the wafer W having undergone the etching processing is carried out from the spin chuck 301.

As has been described, according to this embodiment, an amount of the etching liquid reaching the peripheral edge of the wafer W is relatively small. Hence, not only is it possible to apply the etching processing across the entire bottom surface 9 of the wafer W, but it is also possible to suppress or prevent the etching liquid from flowing over onto the top surface of the wafer W.

Also, because the discharge ports 311 and 312 are disposed at regular intervals, discharge flow rates of the etching liquid discharged directly to the bottom surface 9 of the wafer W from the etching liquid nozzle 307 become almost equal from the center to the peripheral edge of the wafer W. The etching liquid discharged from the respective peripheral discharge ports 312 thus interferes with one another to a moderate degree. Accordingly, an amount of the etching liquid reaching the peripheral edge of the wafer W is further reduced. It is thus possible to further suppress the etching liquid from flowing over onto the top surface of the wafer W.

Further, because an amount of the etching liquid reaching the peripheral edge of the wafer W is relatively small, the etching liquid hardly flows over onto the top surface by running along the plural pinching members 303. It is thus possible to suppress or prevent plural traces of etching (so-called pin marks) from being left along the peripheral edge on the top surface of the wafer W.

FIG. 3 is a plan view of an etching liquid nozzle 407 of a substrate processing apparatus 400 according to another embodiment (second embodiment) of the invention. FIG. 4 is a longitudinal cross section showing the configuration of a major portion of the etching liquid nozzle 407. In the second embodiment, portions corresponding to the respective portions described in the embodiment with reference to FIG. 2 (first embodiment) are labeled with the same reference numerals as those in FIG. 2, and descriptions of these portions are omitted.

As with the etching liquid nozzle 307 of the first embodiment, the etching liquid nozzle 407 of the second embodiment is a long nozzle extending along the rotation radius direction of the wafer W to positions slightly inner than the peripheral edge of the spin base 302 (the positions inner than the end face of the wafer W) by passing through the rotation center C. The etching liquid nozzle 407 is different from the etching liquid nozzle 307 in that a discharge port (rotation shaft discharge port) opposing the rotation center C of the bottom surface 9 of the wafer W is omitted. Larger diameter discharge ports 413 having a larger diameter than the other discharge ports 411 and 412 are disposed at the both ends of the etching liquid nozzle 407. In this point, too, the etching liquid nozzle 407 is different from the etching liquid nozzle 307 of the first embodiment.

A center discharge port 411 disposed at the center of the etching liquid nozzle 407 (a region opposing the center of the wafer W (a region in close proximity to the rotation center C)) and a pair of peripheral discharge port groups 410 disposed with the center in between are provided to the top surface of the etching liquid nozzle 407. Each peripheral discharge port group 410 includes plural peripheral discharge ports 412 and 413 aligned along the shape of the etching liquid nozzle 407 (along the rotation radius direction of the wafer W) on the top surface of the etching liquid nozzle 407.

In this embodiment, the discharge ports 411, 412, and 413 on one side of the etching liquid nozzle 407 (on the right of the etching liquid nozzle 407 in FIG. 3) and those on the other side (on the left of the etching liquid nozzle 407 shown in FIG. 3) are disposed at asymmetric positions. In particular, the center discharge port 411 is disposed at an asymmetric position.

The center discharge port 411 is disposed at a specific interval from the rotation shaft line 1 a of the wafer W. The center discharge port 411 is provided to only one side of the etching liquid nozzle 407, and it is not provided to the other side of the etching liquid nozzle 407. Accordingly, in comparison with other regions of the etching liquid nozzle 407, the discharge ports 411, 412, and 413 are disposed less densely at the center of the etching liquid nozzle 407.

The center discharge port 411 is disposed at a position at which it is possible to supply the etching liquid to the rotation center C of the wafer W owing to spreading of the etching liquid when the etching liquid reaches the bottom surface 9 of the wafer W.

The peripheral discharge ports 412 and 413 are disposed at regular intervals (at the same density) in a region opposing a region of the bottom surface 9 of the wafer W excluding the center thereof (a region between the center and the peripheral edge and the peripheral edge).

The peripheral discharge ports 412 and 413 disposed at the both ends of the etching liquid nozzle 407 are to discharge the etching liquid to the peripheral edge of the wafer W. The peripheral discharge ports 412 and 413 disposed at the both ends of the etching liquid nozzle 407 include plural (two on the right end and three on the left end of the etching liquid nozzle 407 in FIG. 3) larger diameter discharge ports 413 having a larger diameter than the other peripheral discharge ports 412. Referring to FIG. 4, the diameter W2 of the larger diameter discharge ports 413 is set to a size about 1.8 times larger than the diameter W1 of the peripheral discharge ports 412. A discharge flow rate of the etching liquid of the larger diameter discharge ports 413 is thus about 3.2 times higher than a discharge flow rate of the etching liquid of the peripheral discharge ports 412.

The etching liquid nozzle 407 is configured in such a manner that the etching liquid is discharged upward (vertical direction) from the center discharge port 411 and the peripheral discharge ports 412.

On the contrary, a discharge direction of the larger diameter discharge ports 413 is inclined outward in the rotation radius direction of the wafer W at 45 to 60° with respect to the vertical direction. It is thus possible to supply the etching liquid directly to the peripheral edge of the wafer W positioned on the outside of the both ends of the etching liquid nozzle 407 in the rotation direction of the wafer W.

In Example 2 described below in which an experiment for trial production was conducted by the inventor of the present application, the center discharge port 411 was provided at a position 5 mm away from the rotation center. Further, two discharge ports, that is, the outermost and second outermost discharge ports, at the end on one side (on the right in FIG. 3) of the etching liquid nozzle 407 were provided as the larger diameter discharge ports 413, and three discharge ports, that is, the outermost and following two discharge ports, at the end on the other side (on the left in FIG. 3) were provided as the larger diameter discharge ports 413. In addition, in Example 2, the length of the etching liquid nozzle 407 was set to 272 mm, the diameter of the discharge ports 411 and 412 was set to 0.5 mm, the intervals among the discharge ports 411 and 412 were set to 5 mm, and the discharge direction of the larger diameter discharge ports 413 was inclined at 30° with respect to the vertical direction.

During the etching processing, the etching liquid discharged from the center discharge port 411 is supplied directly to the center of the wafer W. The etching liquid discharged from the peripheral discharge ports 412 and 413 is supplied directly to the regions of the wafer W excluding the center thereof. Because the peripheral discharge ports 412 and 413 are disposed at regular intervals, discharge flow rates of the etching liquid discharged directly to the bottom surface 9 of the wafer W are almost equal except for the center of the wafer W.

In the second embodiment, because the discharge flow rates of the etching liquid discharged directly to the bottom surface 9 of the wafer W are almost equal except for the center of the wafer W, the etching liquid discharged from the respective peripheral discharge ports 412 and 413 interferes with one another to a moderate degree. Accordingly, an amount of the etching liquid reaching the peripheral edge of the wafer W is reduced. It is thus possible to suppress the etching liquid from flowing over onto the top surface of the wafer W.

Because the center discharge port 411 is disposed less densely at the center of the etching liquid nozzle 407 than in the other regions of the etching liquid nozzle 407, a discharge flow rate of the etching liquid discharged directly to the center of the bottom surface 9 of the wafer W is lower than the discharge flow rates in the other regions. It is thus possible to suppress an increase of the etching rate at the center of the wafer W where the moving speeds at the respective positions on the bottom surface 9 of the wafer W are relatively slow.

In particular, because the center discharge port 411 is disposed at the position displaced in the rotation radius direction of the wafer W from the position opposing the rotation center C of the bottom surface 9 of the wafer W, it is possible to effectively suppress an increase of the etching rate particularly at the rotation center C of the wafer W.

Further, the discharge flow rates of the larger diameter discharge ports 413 are higher than the discharge flow rates of the other peripheral discharge ports 412. It is therefore possible to suppress a decrease of the etching rate in the peripheral edge of the wafer W where the moving speeds of the respective positions on the bottom surface 9 are relatively fast. It is thus possible to apply the etching processing uniformly across the entire bottom surface 9 of the wafer W.

FIG. 5 is a graph showing the in-plane distribution of etching amounts in etching tests. The abscissa is used for the X-axis coordinate in reference to the rotation center C of the wafer W.

Etching tests were conducted by discharging hydrofluoric acid at 55° C. (concentration: 50 wt %) at a discharge flow rate of 1.0 L/min from etching liquid nozzles of Example 1 and Example 2 described above and Comparative Example described below to the bottom surface (surface on the device forming region side) 9 of the wafer W made of oxide film silicon having an outer diameter of 300 mm and rotating at a rate of 1000 rpm. In the etching tests to measure the in-plane distribution of etching amounts, the etching time was 11 seconds.

The distribution of the etching amount was measured by measuring etching amounts at plural points on a straight line passing through the rotation center C of the wafer W. In FIG. 5, etching amounts were measured at points at every 6.3 mm interval in two opposite directions from the rotation center C of the wafer W.

Comparative Example was a case where the etching test was conducted under the same conditions as described above using a so-called bevel etching liquid nozzle. The configuration of the etching liquid nozzle of Comparative Example is described in United States Patent Application Publication No. US2003/0194878A1 supra.

In a case where the etching liquid nozzle of Example 1 was used, the etching uniformity was 10.56%. In a case where the etching liquid nozzle of Example 2 was used, the etching uniformity was 5.29%. In a case where the etching liquid nozzle of Comparative Example was used, the etching uniformity was 8.98%. The etching uniformity is expressed by Equation (1):

etching uniformity (%)=100×(maximum etching amount−minimum etching amount)/2/average etching amount  (1)

FIG. 6 is a view showing flown over amounts of the etching liquid in etching tests.

Etching tests were conducted under the same conditions as above to measure flown over amounts. In the etching tests to measure the flown over amounts, the etching time was 135 seconds. The etching test was conducted seven times to measure the maximum flown over amount and the average flown over amount in the peripheral edge on the top surface of the wafer W.

In a case where the etching liquid nozzle 307 of Example 1 was used, an average flown over amount was 0.80 mm and the maximum flown over amount was 0.90 mm and no traces of etching were observed in portions abutted on the pinching members 303. In a case where the etching liquid nozzle 407 of Example 2 was used, the average flown over amount was 1.10 mm and the maximum flown over amount was 1.25 mm, and traces of etching of 0.5 mm at the maximum were observed in portions abutted on the pinching members 303. In a case where the etching liquid nozzle in the related art was used, the average flown over amount was 1.21 mm and the maximum flown over amount was 1.55 mm, and traces of etching of 1.55 mm at the maximum were observed in portions abutted on the pinching members 303.

It is understood from FIG. 5 and FIG. 6 that flowing over onto the top surface of the wafer W was suppressed particularly in a case where the etching liquid nozzle 307 of Example 1 was used. Also, it is understood that not only was it possible to suppress the flowing over onto the top surface of the wafer W, but it was also possible to achieve excellent in-plane uniformity by etching in a case where the etching liquid nozzle 407 of Example 2 was used.

FIG. 7 is a plan view of a spin chuck in a substrate processing apparatus 500 according to still another embodiment (third embodiment) of the invention. In the third embodiment, portions corresponding to the respective portions described in the first embodiment above are labeled with the same reference numerals as those in FIG. 1 and FIG. 2, and descriptions of these portions are omitted. In the third embodiment, an etching liquid nozzle 507 is not in the shape of a straight line when viewed in a plane but in the shape of a cross when viewed in a plane.

The etching liquid nozzle 507 has four long array nozzle portions 508 extending radially in the rotation radius direction of the wafer W from the rotation shaft line 1 a of the wafer W, and the respective array nozzle portions 508 are disposed at equiangular intervals of 90°. A rotation shaft discharge port 511 disposed on the rotation shaft line 1 a of the wafer W and plural peripheral discharge ports 512 lined up along the shapes of the respective array nozzle portions 508 (along the rotation radius direction of the wafer W) are provided to the top surface of the etching liquid nozzle 507. A supply channel 513 through which the etching liquid is supplied to the respective discharge ports 511 and 512 is in the shape of a cross extending along the shapes of the respective array nozzle portions 508 and crossing on the rotation shaft line 1 a when viewed in a plane.

Because the etching liquid nozzle 507 has a cross shape when viewed in a plane, an etching liquid at a high temperature is successively supplied directly across the entire bottom surface 9 of the wafer W. It is thus possible to etch away the entire bottom surface 9 of the wafer W at a high etching rate.

While three embodiments have been described, it should be appreciated that the invention is applicable not only to the etching processing for removing an oxide film on the semiconductor wafer W, but also to etching processing for other purposes. Hereinafter, a case where the invention is applied to etching processing for thinning a semiconductor wafer will be described.

FIG. 8 is a cross section schematically showing the configuration of a substrate processing apparatus 100 according to still another embodiment (fourth embodiment) of the invention.

For thinning the semiconductor wafer W, for example, hydrofluoric-nitric acid (a mixed liquid of hydrofluoric acid and nitric acid) is used as the etching liquid.

Hydrofluoric-nitric acid is an etching liquid having extremely high etching power. However, it loses its etching power and deteriorates as soon as it exerts an etching action when it comes into contact with a subject subjected to etching. Hence, when the etching processing is applied to the semiconductor wafer using hydrofluoric-nitric acid, only a region brought into a direct contact with fresh hydrofluoric-nitric acid is sufficiently etched away and a region not brought into a direct contact with fresh hydrofluoric-nitric acid is etched away insufficiently. This raises a problem that the etching processing gives rise to in-plane nonuniformity.

Referring to FIG. 8, the substrate processing apparatus 100 is a single substrate process type apparatus to apply etching processing for thinning to the wafer W on the back surface (bottom surface) 10 opposite to the surface (top surface) on the device forming region side. In this embodiment, hydrofluoric-nitric acid (a mixed liquid of hydrofluoric acid and nitric acid) is used as the etching liquid. The wafer W, on the top surface of which devices have been formed, is placed in the substrate processing apparatus 100 with the surface on the device forming region side faced up. The substrate processing apparatus 100 includes a spin chuck 1 as a substrate holding unit that rotates about a vertical rotation shaft line 1 a passing through almost the center of the wafer W while holding the wafer W in an almost horizontal posture.

FIG. 9 is a plan view schematically showing the configuration of the spin chuck 1 in the substrate processing apparatus 100 shown in FIG. 8.

Referring to FIG. 8 and FIG. 9, the spin chuck 1 has a disc-like spin base 2. Plural (six in this embodiment) pinching members 3 are disposed on the top surface of the spin base 2 almost at equiangular intervals along the peripheral edge. The spin base 2 is configured to rotate by being coupled to the top end of a rotation shaft 5 that is rotated by a chuck rotary driving mechanism 4 including a motor. The rotation shaft 5 is a hollow shaft, inside of which an insertion tube 6 is inserted through. The insertion tube 6 is held inside the rotation shaft 5 in a non-rotating state.

An etching liquid nozzle 7 in the shape of a cross when viewed in a plane is disposed on the spin base 2. The etching liquid nozzle 7 has four long array nozzle portions 8 extending radially in the rotation radius direction of the wafer W from the rotation shaft line 1 a, and the respective array nozzle portions 8 are disposed at equiangular intervals of 90°. Distances from the tip ends of the respective array nozzle portions 8 to the rotation shaft line 1 a are all equal, and the tip ends of the respective array nozzle portions 8 are located at positions slightly inner than the end edge of the spin base 2. The etching liquid nozzle 7 is made hollow inside and linked to the insertion tube 6 at the center position at the bottom thereof. The etching liquid nozzle 7 thus remains stationary and will never rotate in association with rotations of the spin base 2.

A rotation shaft discharge port 11 disposed on the rotation shaft line 1 a and plural peripheral discharge ports 12 lined up along the shapes of the respective array nozzle portions 8 (along the rotation radius direction of the wafer W) are provided to the top surface of the etching liquid nozzle 7. The peripheral discharge ports 12 are disposed more densely with distance from the rotation shaft line 1 a of the wafer W. To be more concrete, the peripheral discharge ports 12 are disposed at shorter intervals as distances from the rotation shaft line 1 a increase. A supply channel 13 communicating with the respective discharge ports 11 and 12 is formed inside the etching liquid nozzle 7. The supply channel 13 is in the shape of a cross extending along the shapes of the respective array nozzle portions 8 and crossing on the rotation shaft line 1 a when viewed in a plane.

A circulation channel 14 is formed inside the insertion tube 6 along the rotation shaft line 1 a. The circulation channel 14 communicates with the supply channel 13. An etching liquid is supplied to the circulation channel 14 from an etching liquid supply source via an etching liquid valve 15. Also, deionized water is supplied to the circulation channel 14 from a deionized water supply source via a deionized water valve 16.

According to the configuration as above, by closing the deionized water valve 16 and opening the etching liquid valve 15, it is possible to supply the etching liquid to the rotation shaft discharge port 11 and the peripheral discharge ports 12 of the etching liquid nozzle 7 via the circulation channel 14 and the supply channel 13. Conversely, by closing the etching liquid valve 15 and opening the deionized water valve 16, it is possible to supply deionized water to the rotation shaft discharge port 11 and the peripheral discharge ports 12 of the etching liquid nozzle 7 via the circulation channel 14 and the supply channel 13. In addition, a gas supply channel 17 is defined between the inner wall surface of the rotation shaft 5 formed of a hollow shaft and the outer wall surface of the insertion tube 6. The gas supply tube 17 opens to the top surface of the spin base 2. It is configured in such a manner that a nitrogen gas as an inert gas is supplied to the gas supply channel 17 via a nitrogen gas valve 18.

A disc-shaped shield plate 20 having substantially the same diameter as the wafer W is provided above the spin chuck 1. The shield plate 20 has an opening 19 at the center thereof. A rotation shaft 21 extending along a shaft line common with the rotation shaft line 1 a of the spin chuck 1 is fixed to the top surface of the shield plate 20. The rotation shaft 21 is made hollow, inside of which is formed a gas supply channel 23 that communicates with the opening 19 in the shield plate 20 and thereby supplies a nitrogen gas toward the center of the wafer W. It is configured in such a manner that a nitrogen gas is supplied to the gas supply channel 23 via a nitrogen gas valve 24.

The rotation shaft 21 is provided with a shield plate elevation driving mechanism 25 to move the shield plate 20 up and down between a proximity position at which the shield plate 20 comes in close proximity to the top surface of the wafer W held by the spin chuck 1 and an evacuation position at which the shield plate 20 evacuates far above the spin chuck 1, and a shield plate rotary driving mechanism 26 to rotate the shield plate 20 almost in sync with rotations of the wafer W by the spin chuck 1.

Hereinafter, etching processing applied to the bottom surface 10 of the wafer W by the substrate processing apparatus 100 will be described.

Before the wafer W subjected to processing is carried into the substrate processing apparatus 100, the shield plate 20 is located at the evacuation position at which it evacuates far above the spin chuck 1 so as not to interrupt a carry-in operation.

In order to process the wafer W, the wafer W is first carried into the substrate processing apparatus 100 by an unillustrated delivery robot, and the wafer W is held by the spin base 2 of the spin chuck 1 with the surface on the device forming region side faced up. When the wafer W is held by the spin base 2, the chuck rotary driving mechanism 4 is controlled for the spin base 2 to start to rotate the wafer W, and the rotating speed of the wafer W is increased, for example, to 3000 rpm. In this instance, the etching liquid nozzle 7 remains stationary as has been described above and will never rotate in association with rotations of the spin base 2. Also, the shield plate elevation driving mechanism 25 is controlled for the shield plate 20 to move down to the proximity position at which it comes in close proximity to the top surface of the wafer W held by the spin base 2. The shield plate rotary driving mechanism 26 is then controlled for the shield plate 20 to keep rotating in the same direction as the wafer W, while the nitrogen gas valve 24 is opened for a nitrogen gas to be supplied from the opening 19 in the shield plate 20 to a space between the wafer W and the shield plate 20. Accordingly, a current of nitrogen gas flowing outward in the radial direction from the center of the shield plate 20 is produced in the space between the wafer W and the shield plate 20.

When the rotating speed of the wafer W reaches, for example, 3000 rpm, the etching liquid valve 15 is opened, and the etching liquid is discharged from the rotation shaft discharge port 11 and the respective peripheral discharge ports 12 of the etching liquid nozzle 7 toward the bottom surface 10 of the wafer W that is rotating. The nitrogen gas valve 18 is also opened and a nitrogen gas is supplied to a space surrounded by the spin base 2 and the bottom surface 10 of the wafer W. The space surrounded by the spin base 2 and the wafer W is eventually filled with a nitrogen gas.

In this instance, the etching liquid discharged from the rotation shaft discharge port 11 is supplied directly to the center of the wafer W. The etching liquid discharged from the respective peripheral discharge ports 12 is supplied directly to the bottom surface 10 of the wafer W in regions opposing the respective peripheral discharge ports 12. As has been described, the peripheral discharge ports 12 are disposed more densely with distance from the rotation shaft line 1 a of the wafer W. Discharge flow rates of the etching liquid therefore become higher with distance from the rotation shaft line 1 a of the wafer W. Meanwhile, moving speeds of the respective positions on the surface of the wafer W become faster with distance from the rotation shaft line 1 a of the wafer W. Discharge flow rates of the etching liquid per unit area therefore become equal almost across the entire bottom surface 10 of the wafer W. In other words, a fresh etching liquid is supplied uniformly almost across the entire bottom surface 10 of the wafer W that is rotating.

Hydrofluoric-nitric acid used as the etching liquid in this embodiment has extremely high etching power when it is fresh. However, it deteriorates so fast that it loses its etching power almost completely in an instant.

Nevertheless, because a fresh etching liquid is uniformly supplied almost across the wafer W that is rotating, the bottom surface 10 of the wafer W is uniformly etched away at an extremely high etching rate (about 50 μm/min at normal temperature). In addition, because the etching liquid nozzle 7 has a cross shape when viewed in a plane, a fresh etching liquid is successively supplied across the entire bottom surface 10 of the wafer W that is rotating.

Further, because the space surrounded by the spin base 2 and the bottom surface 10 of the wafer W is filled with a nitrogen gas, it is possible to suppress deterioration of the etching liquid supplied to the wafer W.

The etching liquid supplied to the bottom surface 10 of the wafer W flows toward the peripheral edge by running over the bottom surface 10 of the wafer W owing to a centrifugal force induced by rotations of the wafer W and wasted to the outside of the wafer W from the peripheral edge. Because a current of nitrogen gas flowing outward in the radial direction from the center of the shield plate 20 is produced in the space between the wafer W (top surface) and the shield plate 20, the etching liquid flowing toward the peripheral edge of the wafer W will not flow over onto the top surface of the wafer W. It is thus possible to prevent the devices formed on the top surface of the wafer W from being damaged by the etching liquid.

When a predetermined time (for example, ten minutes) has elapsed since the supply of the etching liquid started, the etching liquid valve 15 is closed. The deionized water valve 16 is then opened for deionized water to be supplied across the entire bottom surface 10 of the wafer W from the rotation shaft discharge port 11 and the peripheral discharge ports 12. The rotating speed of the wafer W is reduced, for example, from 3000 rpm to 1500 rpm. In this instance, deionized water discharged from the rotation shaft discharge port 11 is supplied directly to the center of the wafer W. Deionized water discharged from the respective peripheral discharge ports 12 is supplied directly to the bottom surface 10 of the wafer W in regions opposing the respective peripheral discharge ports 12.

Deionized water supplied to the bottom surface 10 of the wafer W flows toward the peripheral edge of the wafer W owing to a centrifugal force induced by rotations of the wafer W. Deionized water is then wasted to the outside from the peripheral edge of the wafer W. The etching liquid adhering onto the bottom surface 10 of the wafer W is thus rinsed away by deionized water.

A current of nitrogen gas flowing outward in the rotation radial direction from the center of the shield plate 20 is produced in the space between the wafer W and the shield plate 20. Accordingly, a mixed liquid of deionized water and the etching liquid flowing toward the peripheral edge of the wafer W will not flow over onto the top surface of the wafer W. It is thus possible to prevent the devices formed on the top surface of the wafer W from being damaged by the etching liquid.

When a predetermined time (for example, 30 seconds) has elapsed since the supply of deionized water started, the deionized water valve 16 is closed to stop the supply of deionized water to the bottom surface 10 of the wafer W. In addition, the nitrogen gas valve 24 is closed and the shield plate elevation driving mechanism 25 is controlled for the shield plate 20 to move up to the evacuation position at which it evacuates far above the spin chuck 1.

The rotating speed of the wafer W is then increased from 1500 rpm to 3000 rpm to apply spin dry processing in which the wafer W is dried by throwing off deionized water adhering onto the surface thereof using a centrifugal force after the water rinse processing. When the spin dry processing is applied over, for example, 120 seconds, the wafer W is stopped rotating, and the wafer W having undergone the etching processing is carried out from the spin chuck 1.

As has been described, according to the fourth embodiment, the etching liquid discharged from the rotation shaft discharge port 11 is supplied directly to the center of the wafer W and the etching liquid discharged from the respective peripheral discharge ports 12 is supplied directly to the bottom surface 10 of the wafer W in portions opposing the respective peripheral discharge ports 12. Because the peripheral discharge ports 12 are disposed more densely with distance from the rotation shaft line 1 a of the wafer W, while the wafer W is rotating, a fresh etching liquid is supplied uniformly almost across the entire bottom surface 10 of the wafer W that is rotating. The etching liquid has extremely high etching power when it is fresh. It is thus possible to apply the etching processing uniformly almost across the entire bottom surface 10 of the wafer W at a high etching rate.

In addition, because the etching liquid nozzle 7 has a cross shape when viewed in a plane, a fresh etching liquid is successively supplied directly across the entire bottom surface 10 of the wafer W. It is thus possible to apply the etching processing to the bottom surface 10 of the wafer W at a high etching rate.

FIG. 10 is a plan view of a spin chuck in a substrate processing apparatus 200 according to still another embodiment (fifth embodiment) of the invention. An etching liquid nozzle 107 of the substrate processing apparatus 200 of the fifth embodiment is different from the etching liquid nozzle 7 of FIG. 4 in that it is not in the shape of a cross when viewed in a plane but it is in the shape of a straight line when viewed in a plane. In other words, the etching liquid nozzle 107 is a long nozzle extending along the rotation radius direction of the wafer W by passing through the rotation shaft line 1 a. The both ends of the etching liquid nozzle 107 extend to positions slightly inner than the peripheral edge of the spin base 2.

A rotation shaft discharge port 111 disposed in a region opposing the rotation center C of the wafer W and plural peripheral discharge ports 112 lined up along the shape of the etching liquid nozzle 107 (along the rotation radius direction of the wafer W) are provided to the top surface of the etching nozzle 107. As with the peripheral discharge ports 12 of FIG. 9, the peripheral discharge ports 112 are disposed more densely (at short intervals) with distance from the rotation shaft center C of the wafer W. Hence, while the wafer W is rotating, discharge flow rates of the etching liquid per unit area become equal almost across the entire bottom surface 10 of the wafer W. A fresh etching liquid is thus supplied uniformly almost across the entire bottom surface 10 of the wafer W that is rotating.

While five embodiments have been described, it should be appreciated that the invention can be implemented in still another embodiment. For example, the etching liquid nozzle 507 having a cross shape when viewed in a plane in the third embodiment above may be configured in such a manner that the discharge port is not provided at the position opposing the rotation center C of the wafer W as with the etching liquid nozzle 407 in the second embodiment above. Also, as with the etching liquid nozzle 407 of the second embodiment, larger diameter discharge ports having a larger diameter than the other discharge ports may be provided to the both ends of the etching liquid nozzle 507.

The substrate processing apparatus 100 and 200 in the fourth and fifth embodiments above, respectively, are configured in such a manner that an etching liquid at normal temperature is discharged from the respective discharge ports 11 and 12 and the respective discharge ports 111 and 112 provided to the etching liquid nozzles 7 and 107, respectively. However, as in the first embodiment above, they may be provided with a heater to heat the etching liquid to be discharged from the respective discharge ports 11 and 12 and the respective discharge ports 111 and 112 provided to the etching liquid nozzles 7 and 107, respectively.

The etching liquid nozzles 7 and 107 of the fourth and fifth embodiments, respectively, may be configured in such a manner that density of the discharge ports is increased with distance from the rotation center C by increasing the number of aligned lines with distance from the rotation center C. Alternatively, the etching liquid nozzle may be formed in the shape of a disc opposing the bottom surface 10 of the wafer W to distribute the discharge ports homogeneously on the top surface thereof.

The respective embodiments above have described cases where the etching liquid nozzles 7, 107, 307, 407, and 507 are in the shape of a cross or in the shape of a straight line when viewed in a plane. However, the etching liquid nozzle may extend radially in an arbitrary number of directions at equiangular intervals, for example, in three, five, six, seven, or eight directions extending outward in the rotation radius direction from the rotation center C when viewed in a plane. Further, the etching liquid nozzles may have a length extending in one rotation radius direction of the wafer W from the rotation center C (that is, a length about the half of the etching liquid nozzles 307, 407, and 107 shown in FIG. 2, FIG. 3, and FIG. 10, respectively).

The respective embodiments have described a case where the peripheral discharge ports 312, 412, 413, 512, 12, and 112 are formed in a line in the rotation radius direction. However, the peripheral discharge ports 312, 412, 413, 512, 12, and 112 may be formed in more than one line.

Further, the etching liquid nozzles 307, 407, 507, 7, and 107 may be configured to be rotatable about the rotation shaft line 1 a together with the insertion tubes 306 and 6, so that the etching liquid is discharged toward the wafer W from the etching liquid nozzles 307, 407, 507, 7, and 107 that are rotating.

While the embodiments of the invention have been described in detail, it should be appreciated that these embodiments represent examples to provide clear understanding of the technical contents of the invention, and the invention is not limited to these examples. The sprit and the scope of the invention, therefore, are limited solely by the scope of the appended claims.

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-276502 filed with the Japanese Patent Office on Oct. 10, 2006 and the prior Japanese Patent Application No. 2007-41313 filed with the Japanese Patent Office on Feb. 21, 2007, the entire contents of which are incorporated herein by reference. 

1. A substrate processing apparatus, comprising: a substrate holding unit that holds a substrate almost in a horizontal posture: a rotating unit that rotates the substrate held by the substrate holding unit about a vertical shaft line; and an etching liquid nozzle disposed oppositely to a bottom surface of the substrate held by the substrate holding unit and having plural discharge ports each having a different distance from a rotation center of the substrate rotated by the rotating unit so as to discharge an etching liquid toward the bottom surface of the substrate rotated by the rotating unit from the plural discharge ports.
 2. The substrate processing apparatus according to claim 1, wherein: the plural discharge ports of the etching liquid nozzle are provided in such a manner that discharge flow rates of the etching liquid per unit area on the bottom surface of the substrate that is being rotated by the rotating unit become equal almost entirely across the bottom surface of the substrate.
 3. The substrate processing apparatus according to claim 1, wherein: the plural discharge ports of the etching liquid nozzle are aligned along a rotation radius direction of the substrate rotated by the rotating unit.
 4. The substrate processing apparatus according to claim 1, wherein: the plural discharge ports of the etching liquid nozzle are disposed more densely with distance from the rotation center of the substrate rotated by the rotating unit.
 5. The substrate processing apparatus according to claim 1, wherein: the plural discharge ports of the etching liquid nozzle are aligned along a rotation radius direction at almost same density so as to oppose a region from a center to a peripheral edge of the substrate rotated by the rotating unit.
 6. The substrate processing apparatus according to claim 1, wherein: the plural discharge ports of the etching liquid nozzle include plural peripheral discharge ports aligned along a rotation radius direction almost at same density so as to oppose a region of the substrate rotated by the rotating unit excluding a center thereof.
 7. The substrate processing apparatus according to claim 5, wherein: the plural discharge ports include a discharge port for peripheral edge to supply the etching liquid to a peripheral edge of the substrate rotated by the rotating unit and plural inner discharge ports disposed closer to the rotation center of the substrate than the discharge port for peripheral edge; and the discharge port for peripheral edge includes a larger diameter discharge port having a larger diameter than the inner discharge ports.
 8. The substrate processing apparatus according to claim 5, wherein: the plural discharge ports include a discharge port for peripheral edge to supply the etching liquid to a peripheral edge of the substrate rotated by the rotating unit; and the discharge port for peripheral edge has an inclined discharge port that discharges the etching liquid in a direction inclined outward in a radius direction of the substrate with respect to a vertical direction.
 9. The substrate processing apparatus according to claim 6, wherein: the plural discharge ports include a discharge port for peripheral edge to supply the etching liquid to a peripheral edge of the substrate rotated by the rotating unit and plural inner discharge ports disposed closer to the rotation center of the substrate than the discharge port for peripheral edge; and the discharge port for peripheral edge includes a larger diameter discharge port having a larger diameter than the inner discharge ports.
 10. The substrate processing apparatus according to claim 6, wherein: the plural discharge ports include a discharge port for peripheral edge to supply the etching liquid to a peripheral edge of the substrate rotated by the rotating unit; and the discharge port for peripheral edge has an inclined discharge port that discharges the etching liquid in a direction inclined outward in a radius direction of the substrate with respect to a vertical direction.
 11. The substrate processing apparatus according to claim 1, further comprising: an etching liquid heating unit that heats the etching liquid to be discharged from the plural discharge ports of the etching liquid nozzle.
 12. The substrate processing apparatus according to claim 1, wherein: the substrate holding unit includes plural holding members that hold the substrate almost in the horizontal posture in cooperation by abutting on a peripheral edge of the substrate at different positions. 